Long focal length optical projection assembly

Abstract

This invention provides a long-focal-length optical projection assembly, which consists of an aperture and multiple lenses from the object side to the image side. The multiple lenses are a first lens with positive optical power, a second lens with negative optical power, a third lens with positive optical power, a fourth lens with positive optical power, and a fifth lens with negative optical power. The object side of the first lens is aspherical, the second lens is a biconcave lens, the third lens is a meniscus lens with its concave surface facing the object side, and both sides of the fourth and fifth lenses are aspherical. Through specific optical power allocation and the use of aspherical lenses, distortion is controlled to an extremely low level (<0.2%), ensuring accurate fusion of the projected image with the real scene. At the same time, different material combinations are used in the relevant lenses to achieve apochromatic achromatic aberration across the entire visible light spectrum, eliminating color ghosting and improving the fidelity of the image display.

Description

Technical Field

[0001] This invention relates to an optical projection assembly, and more particularly to a long focal length optical projection assembly. Background Technology

[0002] To achieve precise fusion of virtual images and the road environment, optical projection components need to match the far-field visual accommodation mechanism of the human eye by projecting virtual images at greater distances, and to meet the perception requirements of advanced autonomous driving. On the one hand, to avoid the driver frequently switching their focus due to virtual images that are too close, thus causing distraction and safety hazards, the optical projection components must have a long focal length to project the virtual image into the far-field area beyond the windshield. On the other hand, to match the perception requirements of L3 / L4 level autonomous driving, the virtual image display distance needs to be extended from the traditional vehicle status information within a few meters to Advanced Driver Assistance System (ADAS) warning information at tens of meters, and further extended to hundreds of meters, thereby achieving virtual-real fusion with distant road elements such as lane lines. Augmented reality head-up display systems do not actually project images onto the distant road surface, but rather, through precise optical design, allow the driver to perceive a virtual image presented on the road ahead, thus achieving fusion with the real scene. Although the virtual image is at a greater distance, the physical optical path of the optical projection components is still controlled within a limited range.

[0003] To achieve the above functions, the optical projection components of augmented reality head-up display systems face stringent optical requirements: First, they must have a long focal length to achieve virtual image distances of tens or even hundreds of meters, meeting the projection needs of far-field augmented reality information; second, they must be able to effectively correct chromatic aberration in a wide visible light band to avoid halos at the edges of color images and ensure display quality; third, they must have high resolution, low aberration, and low distortion to ensure that projected elements such as navigation arrows and warning signs are accurately aligned with real lane lines; and fourth, they must strictly control the image-side telecentricity to match the coupling efficiency of the optical waveguide, while achieving a miniaturized design to adapt to the limited space layout of the dashboard.

[0004] Chinese invention patent publication number "CN116736533A" discloses a projection lens and display system for a waveguide-type augmented reality head-up display system. It uses five single lenses to achieve high resolution (MTF 0.5@125Lp / mm) and low aberration (field curvature ±0.05mm, distortion 0.2%), and achieves a small size (aperture 10mm, total length 15mm). However, it does not consider the impact of chromatic aberration in the wide visible light band on the projected image effect, and the focal length is relatively short (f=6~10mm), making it only suitable for projection scenarios with a relatively short working distance.

[0005] Chinese invention patent publication number "CN119335687A" discloses a projection lens and head-up display system. It uses five single lenses to achieve ultra-thin and miniaturized lens (16mm aperture, 30mm total length) and has a long focal length (34mm), enabling an imaging range from 2m to infinity. At the same time, it controls the chromatic aberration to 0.3 pixels (0.0015mm) and has high imaging resolution (MTF0.6@66Lp / mm). However, the optical system has an aberration distortion of 0.4%, which results in insufficient overlap between the projected image and the real road background at different viewing angles at long distances, which reduces the accuracy of projection path guidance. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a long focal length optical projection component with high resolution, long focal length, and low aberration and low chromatic aberration.

[0007] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: a long focal length optical projection component, which consists of an aperture and multiple lenses from the object side to the image side. The multiple lenses are a first lens with positive optical power, a second lens with negative optical power, a third lens with positive optical power, a fourth lens with positive optical power, and a fifth lens with negative optical power. The object side surface of the first lens is aspherical, the second lens is a biconcave lens, the third lens is a meniscus lens with its concave surface facing the object side, and both sides of the fourth and fifth lenses are aspherical. The radius of curvature R32 of the image side surface of the third lens and the radius of curvature R41 of the object side surface of the fourth lens satisfy: -1. 3≤R32 / R41≤-0.9, the focal length f of the long focal length optical projection component, the focal length f1 of the first lens, the focal length f2 of the second lens, the focal length f3 of the third lens, the focal length f4 of the fourth lens, and the focal length f5 of the fifth lens satisfy: 45mm<f<65mm, 0.8<f1 / f<1.0, -0.6<f2 / f<-0.3, 0.7<f3 / f<2.1, 0.5<f4 / f<0.7, -0.8<f5 / f<-0.5, and the Abbe number Vd4 of the fourth lens and the Abbe number Vd5 of the fifth lens satisfy: 30<Vd4-Vd5<45.

[0008] Compared with the prior art, the advantages of the present invention are that by using specific optical power allocation and aspherical lenses, distortion is controlled to a very low level (<0.2%), ensuring accurate fusion of the projected image with the real scene; at the same time, different material combinations are used in the relevant lenses to achieve achromatic aberration across the entire visible light spectrum, eliminating color ghosting and improving the fidelity of the image display.

[0009] In one feasible implementation, both the second and third lenses have aspherical surfaces on both sides.

[0010] In one feasible implementation, the radius of curvature R41 of the object side of the fourth lens, the radius of curvature R42 of the image side of the fourth lens, the radius of curvature R51 of the object side of the fifth lens, and the radius of curvature R52 of the image side of the fifth lens satisfy: 0.3≤|R41 / R42|≤1.0, 0.1≤|R52 / R51|≤0.5.

[0011] In one feasible implementation, the total optical length (TTL) of the long focal length optical projection component satisfies: 90mm < TTL < 120mm.

[0012] In one feasible implementation, the first lens is a cemented lens composed of a first single lens with negative optical power, a second single lens with positive optical power, and a third single lens with negative optical power. The focal lengths f11 of the first single lens, f12 of the second single lens, and f13 of the third single lens satisfy the following: -16.5 < f11 / f1 < -11.5, 0.5 < f12 / f1 < 0.7, and -2.0 < f13 / f1 < -1.8.

[0013] In one feasible implementation, the Abbe number Vd11 of the first single lens, the Abbe number Vd12 of the second single lens, and the Abbe number Vd13 of the third single lens satisfy: 13 < Vd11 - Vd12 < 15, 23 < Vd12 - Vd13 < 26.

[0014] In one feasible implementation, the first lens is a cemented doublet composed of a fourth single lens with positive optical power and a fifth single lens with negative optical power, wherein the focal length f14 of the fourth single lens and the focal length f15 of the fifth single lens satisfy: 0.5 < f14 / f1 < 0.7, -1.8 < f15 / f1 < -1.3.

[0015] In one feasible implementation, the Abbe number Vd14 of the fourth single lens and the Abbe number Vd15 of the fifth single lens satisfy: 19 < Vd14 - Vd15 < 23. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the optical structure of Example 1 of the present invention;

[0017] Figure 2 This is a graph of the optical modulation transfer function of Example 1 of the present invention;

[0018] Figure 3This is a vertical axis color difference curve diagram of Example 1 of the present invention;

[0019] Figure 4 This is a distortion curve diagram of Example 1 of the present invention;

[0020] Figure 5 This is a schematic diagram of the optical structure of Example 2 of the present invention;

[0021] Figure 6 This is a graph of the optical modulation transfer function of Example 2 of the present invention;

[0022] Figure 7 This is a vertical color difference curve diagram of Example 2 of the present invention;

[0023] Figure 8 This is a distortion curve diagram of Example 2 of Embodiment 2 of the present invention;

[0024] Figure 9 This is a schematic diagram of the optical structure of Example 3 of the present invention;

[0025] Figure 10 This is a graph of the optical modulation transfer function of Example 3 of the present invention;

[0026] Figure 11 This is a vertical axis color difference curve diagram of Example 3 of the present invention;

[0027] Figure 12 This is a distortion curve diagram of Example 3 of Embodiment 3 of the present invention;

[0028] Figure 13 This is a schematic diagram of the optical structure of Example 4 of the present invention;

[0029] Figure 14 This is a graph of the optical modulation transfer function of Example 4 of the present invention;

[0030] Figure 15 This is a vertical axis color difference curve diagram of Example 4 of the present invention;

[0031] Figure 16 This is a distortion curve diagram of Example 4 of the present invention. Detailed Implementation

[0032] The following description, in conjunction with the accompanying drawings, illustrates specific examples of the present invention. The drawings are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention.

[0033] In the accompanying drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for ease of illustration. The drawings are for illustrative purposes only and are not strictly to scale. The waveguide-type augmented reality head-up display system is used in automotive head-up display systems. Its structure includes an image generation unit, a waveguide unit, and more specifically, the image generation unit may include a light source, a silicon-based liquid crystal display unit, a relay system, and other optical components. The long-focal-length optical projection component in the relay system primarily serves to magnify the image.

[0034] Example: Figure 1 , Figure 5 , Figure 9 and Figure 13 As shown, a long-focal-length optical projection assembly comprises, from the object side to the image side, an aperture stop STO, a first lens L1 with positive optical power, a second lens L2 with negative optical power, a third lens L3 with positive optical power, a fourth lens L4 with positive optical power, and a fifth lens L5 with negative optical power. The aperture stop STO is located at the very front of the long-focal-length optical projection assembly, serving as a front aperture stop. This front placement of the aperture stop allows the long-focal-length optical projection assembly to have a longer projection distance, improving the interactive effect of the head-up display. The third lens L3 and the fourth lens L4 both have positive optical power, enabling secondary beam collection and adjusting the light propagation direction of each field of view at the highest point of the light beam, reducing aberrations and improving image quality.

[0035] To improve image quality and reduce aberrations in long-focal-length optical projection components, aspherical lenses can be used, whose surface shape satisfies the following equation:

[0036] ,

[0037] Where y represents the radial coordinate value of the lens perpendicular to the optical axis. The distance from the vertex of the aspherical lens to the optical axis at a height of y is the sag. c = 1 / R, where R represents the radius of curvature at the center of the aspherical lens surface, k represents the conic coefficient, and parameters B, C, and D are the coefficients of the 4th, 6th, and 8th order terms of the higher-order aspherical polynomial. In this embodiment, the object surface of the first lens L1 is aspherical, which allows for control of the ray direction in each field of view while collecting the light beam, reducing aberrations and improving imaging performance. To precisely control the ray direction in each field of view, reduce aberrations, and improve imaging performance, both sides of the fourth lens L4 and the fifth lens L5 can be set aspherical.

[0038] The second lens, L2, is a biconcave lens. It provides a larger optical power by diverging the collected light beam, allowing subsequent lenses to adjust for distortion and other aberrations, while also increasing the focal length. The third lens, L3, is a meniscus lens with its concave side facing the object side. It can converge light in a small amount, reducing lens sensitivity and aberrations. The image-side radius of curvature R32 of the third lens L3 and the object-side radius of curvature R41 of the fourth lens satisfy the condition: -1.3 ≤ R32 / R41 ≤ -0.9. This near-symmetrical arrangement of the two surfaces allows for a smooth transition and gradual convergence of light, reducing lens sensitivity and improving image quality.

[0039] To control the long-focal-length optical projection component and achieve virtual image projection over a longer range, the focal length f of the long-focal-length optical projection component must satisfy: 45mm < f < 65mm. To reduce lens tolerance sensitivity and achieve high-quality imaging, the optical power of each lens can be rationally allocated, controlling the focal lengths f1 of the first lens L1, f2 of the second lens L2, f3 of the third lens L3, f4 of the fourth lens L4, and f5 of the fifth lens L5 to satisfy: 45mm < f < 65mm, 0.8 < f1 / f < 1.0, -0.6 < f2 / f < -0.3, 0.7 < f3 / f < 2.1, 0.5 < f4 / f < 0.7, -0.8 < f5 / f < -0.5.

[0040] By controlling the Abbe number Vd4 of the fourth lens L4 and the Abbe number Vd5 of the fifth lens L5 to satisfy: 30 < Vd4 - Vd5 < 45, chromatic aberration can be balanced in high-light conditions and overcorrection can be avoided.

[0041] In one embodiment, in order to more accurately control the ray trajectory of each field of view, reduce aberrations, and improve imaging performance, both sides of the second lens L2 and the third lens L3 are aspherical.

[0042] In one embodiment, the curvature radii R41 of the object side of the fourth lens L4, R42 of the image side of the fourth lens L4, R51 of the object side of the fifth lens L5, and R52 of the image side of the fifth lens L5 satisfy: 0.3≤|R41 / R42|≤1.0, 0.1≤|R52 / R51|≤0.5. This setting can better control the convergence of light to form an image, while allowing the light to transition smoothly between the fourth lens L4 and the fifth lens L5, reducing lens sensitivity, controlling the light imaging angle, and reducing image telecentrism.

[0043] In one embodiment, the total optical length (TTL) of the long-focal-length optical projection component satisfies: 90mm < TTL < 120mm. By achieving a longer focal length to support long-distance projection while compressing the total optical length to within 120mm, the industry problem of bulky projection size in head-up display systems is solved. These innovations effectively address the pain point of the inability to simultaneously achieve projection distance, image quality, and miniaturization in existing technologies, providing crucial optical support for highly immersive augmented reality head-up display systems.

[0044] In such Figure 1 and Figure 5 In the illustrated embodiment, the first lens L1 is a cemented three-lens lens composed of a first single lens L11 with negative optical power, a second single lens L12 with positive optical power, and a third single lens L13 with negative optical power. The focal lengths f11 of the first single lens L11, f12 of the second single lens L12, and f13 of the third single lens L13 satisfy the following: -16.5 < f11 / f1 < -11.5, 0.5 < f12 / f1 < 0.7, and -2.0 < f13 / f1 < -1.8. Reasonably distributing the optical power in the cemented three-lens lens can effectively control distortion and chromatic aberration, thereby improving imaging performance. The Abbe numbers Vd11 of the first single lens L11, Vd12 of the second single lens L12, and Vd13 of the third single lens L13 satisfy: 13 < Vd11 - Vd12 < 15, 23 < Vd12 - Vd13 < 26. Controlling the above parameters can produce different deflection angles for light of different wavelengths, and the chromatic aberration of multiple single lenses after cementation can cancel each other out.

[0045] In such Figure 9 and Figure 13 In the illustrated embodiment, the first lens L1 is a cemented doublet composed of a fourth single lens L14 with positive optical power and a fifth single lens L15 with negative optical power. The focal lengths f14 and f15 of the fourth and fifth single lenses L14 and L15 respectively satisfy: 0.5 < f14 / f1 < 0.7, -1.8 < f15 / f1 < -1.3. By rationally allocating the optical power in the cemented doublet, distortion and chromatic aberration can also be controlled, improving imaging performance. The Abbe number Vd14 of the fourth single lens L14 and Vd15 of the fifth single lens L15 satisfy: 19 < Vd14 - Vd15 < 23. Controlling these parameters can also cause different wavelengths of light to produce different deflection angles, and the chromatic aberration after multiple single lenses are cemented together can cancel each other out.

[0046] The following are four specific examples provided by embodiments of the present invention.

[0047] Example 1:

[0048] like Figure 1As shown, the long focal length optical projection assembly consists of an aperture stop STO, a first single lens L11, a second single lens L12, a third single lens L13, a second lens L2, a third lens L3, a fourth lens L4, and a fifth lens L5. The first single lens L11, the second single lens L12, and the third single lens L13 are cemented together to form the first lens L1.

[0049] The main optical structural parameters of this Example 1 are shown in Table 1:

[0050] Table 1

[0051]

[0052] The parameters of the aspherical structure in Example 1 are shown in Table 2:

[0053] Table 2

[0054]

[0055] Figure 2 This is the optical modulation transfer function curve of Example 1. At 100 Lp / mm, the MTF of the central field of view (0° meridian / 0° sagittal) is >0.65, and the MTF of the edge field of view (7.5° meridian / 7.5° sagittal) is >0.4, indicating good imaging performance.

[0056] Figure 3 This is the vertical axis color difference curve of Example 1. The color difference is within the Airy disk range, and the color difference is well corrected.

[0057] Figure 4 The distortion curve for Example 1 shows a distortion of 0.1708%, which is kept to a minimum level (<0.2%).

[0058] Example 2:

[0059] like Figure 5 As shown, the long focal length optical projection assembly consists of an aperture stop STO, a first single lens L11, a second single lens L12, a third single lens L13, a second lens L2, a third lens L3, a fourth lens L4, and a fifth lens L5. The first single lens L11, the second single lens L12, and the third single lens L13 are cemented together to form the first lens L1.

[0060] Compared to Example 1, in Example 2, the two surfaces of the second lens L2 and the third lens L3 become aspherical, resulting in improved MTF and illuminance, but slightly increased distortion and field curvature.

[0061] The main optical structural parameters of Example 2 are shown in Table 3:

[0062] Table 3

[0063]

[0064] The parameters of the aspherical structure in Example 2 are shown in Table 4:

[0065] Table 4

[0066]

[0067] Figure 6 This is the optical modulation transfer function curve of Example 2. At 100 Lp / mm, the MTF of the central field of view (0° meridian / 0° sagittal) is >0.65, and the MTF of the edge field of view (7.5° meridian / 7.5° sagittal) is >0.45, indicating good imaging performance.

[0068] Figure 7 This is the vertical axis color difference curve for Example 2. The color difference is within the Airy disk range, and the color difference is well corrected.

[0069] Figure 8 The distortion curve for Example 2 is 0.1901%, which is controlled at a very low level (<0.2%).

[0070] Example 3:

[0071] like Figure 9 As shown, the long focal length optical projection assembly consists of an aperture stop STO, a fourth single lens L14, a fifth single lens L15, a second lens L2, a third lens L3, a fourth lens L4, and a fifth lens L5. The fourth single lens L14 and the fifth single lens L15 are cemented together to form the first lens L1.

[0072] Compared to Example 1, in Example 3, the first lens L1 is changed from triplet to doublet, the optical power of the third lens L3 is reduced, and the MTF and illuminance are improved.

[0073] The main optical structural parameters of Example 3 are shown in Table 5:

[0074] Table 5

[0075]

[0076] The parameters of the aspherical structure in Example 3 are shown in Table 6:

[0077] Table 6

[0078]

[0079] Figure 10 This is the optical modulation transfer function curve of Example 3. At 100 Lp / mm, the MTF of the central field of view (0° meridion / 0° sagitta) is >0.7, and the MTF of the edge field of view (7.5° meridion / 7.5° sagitta) is >0.5, indicating good imaging performance.

[0080] Figure 11This is the vertical axis color difference curve of Example 3. The color difference is within the Airy disk range, and the color difference is well corrected.

[0081] Figure 12 The distortion curve for Example 3 shows a distortion of 0.1868%, which is kept to a minimum level (<0.2%).

[0082] Example 4:

[0083] like Figure 13 As shown, the long focal length optical projection assembly consists of an aperture stop STO, a fourth single lens L14, a fifth single lens L15, a second lens L2, a third lens L3, a fourth lens L4, and a fifth lens L5. The fourth single lens L14 and the fifth single lens L15 are cemented together to form the first lens L1.

[0084] Compared to Example 3, in Example 4, the two surfaces of the second lens L2 and the third lens L3 become aspherical, thus improving the MTF.

[0085] The main optical structural parameters of Example 4 are shown in Table 7:

[0086] Table 7

[0087]

[0088] The parameters of the aspherical structure in Example 4 are shown in Table 8:

[0089] Table 8

[0090]

[0091] Figure 14 This is the optical modulation transfer function curve of Example 4. At 100 Lp / mm, the MTF of the central field of view (0° meridian / 0° sagittal) is >0.7, and the MTF of the edge field of view (7.5° meridian / 7.5° sagittal) is >0.75, indicating good imaging performance.

[0092] Figure 15 This is the vertical axis color difference curve of Example 4. The color difference is within the Airy disk range, and the color difference is well corrected.

[0093] Figure 16 The distortion curve for Example 4 shows a distortion of 0.1963%, which is kept to a minimum level (<0.2%).

[0094] The specific performance parameters for the four examples above are shown in Table 9:

[0095] Table 9

[0096]

[0097] The examples shown above are merely individual examples of the present invention and do not limit the scope of protection of the present invention. Therefore, equivalent changes made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A long-focal-length optical projection assembly, comprising an aperture stop and multiple lenses from the object side to the image side, characterized in that, The plurality of lenses are a first lens with positive optical power, a second lens with negative optical power, a third lens with positive optical power, a fourth lens with positive optical power, and a fifth lens with negative optical power. The object-side surface of the first lens is aspherical, the second lens is a biconcave lens, the third lens is a meniscus lens with its concave surface facing the object side, and both sides of the fourth and fifth lenses are aspherical. The radius of curvature R32 of the image-side surface of the third lens and the radius of curvature R41 of the object-side surface of the fourth lens satisfy: -1.3 ≤ R32 / R41 ≤ -0.

9. This is a long-focal-length optical projection. The focal length f of the component, the focal length f1 of the first lens, the focal length f2 of the second lens, the focal length f3 of the third lens, the focal length f4 of the fourth lens, and the focal length f5 of the fifth lens satisfy the following: 45mm < f < 65mm, 0.8 < f1 / f < 1.0, -0.6 < f2 / f < -0.3, 0.7 < f3 / f < 2.1, 0.5 < f4 / f < 0.7, -0.8 < f5 / f < -0.

5. The Abbe number Vd4 of the fourth lens and the Abbe number Vd5 of the fifth lens satisfy the following: 30 < Vd4 - Vd5 < 45.

2. The long focal length optical projection component as described in claim 1, characterized in that, Both sides of the second lens and the third lens are aspherical.

3. The long focal length optical projection component as described in claim 1, characterized in that, The object-side radius of curvature R41 of the fourth lens, the image-side radius of curvature R42 of the fourth lens, the object-side radius of curvature R51 of the fifth lens, and the image-side radius of curvature R52 of the fifth lens satisfy: 0.3≤|R41 / R42|≤1.0, 0.1≤|R52 / R51|≤0.

5.

4. The long focal length optical projection component as described in claim 1, characterized in that, The total optical length (TTL) of the long focal length optical projection component satisfies: 90mm < TTL < 120mm.

5. A long focal length optical projection component as described in any one of claims 1 to 4, characterized in that, The first lens is a cemented lens composed of a first single lens with negative optical power, a second single lens with positive optical power, and a third single lens with negative optical power. The focal lengths f11 of the first single lens, f12 of the second single lens, and f13 of the third single lens satisfy the following: -16.5 < f11 / f1 < -11.5, 0.5 < f12 / f1 < 0.7, and -2.0 < f13 / f1 < -1.

8.

6. A long focal length optical projection component as described in claim 5, characterized in that, The Abbe number Vd11 of the first single lens, the Abbe number Vd12 of the second single lens, and the Abbe number Vd13 of the third single lens satisfy the following: 13 < Vd11 - Vd12 < 15, 23 < Vd12 - Vd13 < 26.

7. A long focal length optical projection assembly as described in any one of claims 1 to 4, characterized in that, The first lens is a cemented doublet composed of a fourth single lens with positive optical power and a fifth single lens with negative optical power. The focal length f14 of the fourth single lens and the focal length f15 of the fifth single lens satisfy: 0.5 < f14 / f1 < 0.7, -1.8 < f15 / f1 < -1.

3.

8. A long focal length optical projection assembly as described in claim 7, characterized in that, The Abbe number Vd14 of the fourth single lens and the Abbe number Vd15 of the fifth single lens satisfy: 19 < Vd14 - Vd15 < 23.

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